Howard – I used the email I can see here, being a mod/admin, which you signed up with (it’s in your profile). Just re-sent the email.
Peter wrote:
A structural change? Cutting a hole in the leading edge.
The fact that the other wing already has this apparently doesn’t change that. Somebody looked into this some years ago.
Are you sure about this? A lot of Part 21 bla bla / minor / major mod suggestions made on this forum are incorrect. I would be amazed if it wasn’t possible as minor mod? Did someone who does minor mods often apply for this, and got it denied?
Are you sure about this?
No, I am not sure, but based on everything I have seen in 13 years this is what I think.
For example, some years ago when I was on G-reg I wanted to install a second (backup) oil pressure gauge, and this was assessed by a CAA Level 2 firm as Major, and quoted at some four figures even if I did the whole design, right down to choosing the connectors in the wiring. Under FAA that is unquestionably a Minor (no “change to the basic design of…”) and I have that from 2 × DAR, 1 × DER, about 3 x IA.
FWIW, a US FSDO ruled the lights cluster is a Major, hence the guy with the TB10 doing a Field Approval.
A lot of Part 21 bla bla / minor / major mod suggestions made on this forum are incorrect
All corrections from experts are always welcome 
But it also could be that the posts which you think are wrong are just a reflection of the ways in which the 2 or 3 UK Part 21 firms (active in GA) work. There is almost no money in Minor mods. As an example, one of them wanted GBP 2k + VAT for a DER package for mounting the TAS 605 box in the boot of my N-reg TB20! I went elsewhere… I later heard from a former Part 21 guy that this DER route is used to obtain an EASA STC (EASA accepts US DER data) which can then be sold over and over. So I think there are all sorts of issues going on here…
Peter wrote:
But it also could be that the posts which you think are wrong are just a reflection of the ways in which the 2 or 3 UK Part 21 firms (active in GA) work. There is almost no money in Minor mods. As an example, one of them wanted GBP 2k + VAT for a DER package for mounting the TAS 605 box in the boot of my N-reg TB20! I went elsewhere… I later heard from a former Part 21 guy that this DER route is used to obtain an EASA STC (EASA accepts US DER data) which can then be sold over and over. So I think there are all sorts of issues going on here…
That is strange as well, a TAS box would be a minor change as well. Did several of them. Once this was free of charge for the EASA fee’s, then it became 250 Euro and now is somewhere around 290 Euro. A minor change owner can also sell the design and approval to others as well. This is the reason I usually change only the 290 Euro amount, and don’t charge for the doing the design work. Later customer will also pay 290 Euro, which makes it a fair price for the 1st and later customers. This why my design work is payed by re-using approvals in combination with a fair low price for all my customers. On some approvals I loose money (work for free to do the approval), on others I can sell multiple times, making more money. It equals pretty well. I think this fair. Some charge a huge amount for the 1St customer, and offer it free of the charge to the 2nd customer, which I think is unfair.
Peter wrote:
For example, some years ago when I was on G-reg I wanted to install a second (backup) oil pressure gauge, and this was assessed by a CAA Level 2 firm as Major, and quoted at some four figures even if I did the whole design, right down to choosing the connectors in the wiring.
I don’t understand this one either, why would it be major? Majors often become in the four figers, having a DOA to make the design. Not worthwhile in most general aviation situations.
The only major designs in my opinion are worthwhile in some limited cases:
Yes – the TAS box is covered by an AML STC. The DER stuff was just for the screws holding it to the airframe, next to the ELT and the stormscope. Drilling holes in an unpressurised hull is is amply covered by the FAA AC-whatever standard repair procedures manual. However, I have heard a local EASA+FAA 145 firm argue that manual is for repairs only, not for any new installs, which is rubbish but one is usually poorly placed to argue except by taking a walk. Also most owners don’t know anything about certification, and just pay…
I asked a local avionics shop about replacing a DG+CDI with a HSI in a C172R. They said that unless we picked a modern EHSI for which there would be an STC (AML, probably), it would be considered a major mod. That sounds completely unreasonable to me?
Airborne_Again wrote:
I asked a local avionics shop about replacing a DG+CDI with a HSI in a C172R. They said that unless we picked a modern EHSI for which there would be an STC (AML, probably), it would be considered a major mod. That sounds completely unreasonable to me?
We are speeking EASA here right?
Again, I don’t see why this would be a major. As extra an often overlooked alternative, you can check if an HSI is optional equipment for your specific aircraft. I don’t have documentation at hand right now, but I think an HSI was one of the options Cessna certified your model with. If so you could use that complete option to install it without any contact with EASA.
That said, I think a “regular” HSI system, such as Bendix/King KCS55 is far to expensive for a new installation. It requires to much wiring with components all over the place, resulting in a lot of labour. An EHSI such as Aspen EFD1000 would make more sense from an economical point of view. The Aspen has just two or three components and requires far less wiring resulting in signification lower installation cost.
Used KCS55 systems are nice for people who allready have a KCS55 system, and would like to have spares, new installation is just to expensive, and for homebuilds much nicer equipment at a lower price is available.
So, how does CS-STAN help (Howard, not Peter) in getting the TB20 outfitted with LED lights (CS-SC031a – EXCHANGE OF CONVENTIONAL ANTI-COLLISION LIGHTS, POSITION LIGHTS AND LANDING & TAXI LIGHTS BY LED TYPE LIGHTS)?
tmo wrote:
So, how does CS-STAN help (Howard, not Peter) in getting the TB20 outfitted with LED lights
CS-STAN is to enable certain standard modifications. It is not the answer to every modification. So in this part, it approves the LED light installation, but doesn’t solve the annunciator issue. So you would need additional approval to modify or remove the annunciators.
